The present invention relates to a device for positioning of a drill bit at a positioning plane. This means that the drill bit or a point near the drill bit is manoeuvred such that it obtains a desired position in the positioning plane.
In existing rock drilling rigs the operator positions the drill bit by the eye. This results in a relatively high uncertainty at the positioning since the operator is far from the tunnel front and normally does not see the drill bit along the drill string. This means the the drill bit will be aligned towards a point to the side of the desired one if the drill bit if the drill bit is not positioned in a well defined lengthwise position. This uncertainty means that one has to take into account at the subsequent blasting that the drill holes are not in optimal positions. This gives as a result that an extra amount of explosives has to be used which makes the driving of the tunnel more expensive.